1. Field of the Invention
The present invention relates generally to drum cutter mining machines, and more particularly, to a rack device for advancing a drum cutter mining machine used in underground mining.
2. Description of the Prior Art
Drum cutter mining machines utilized in shearing operations in long wall mining procedures are well known. Conventionally, the drum cutter mining machine includes at least one, and usually two, circular cutting drums which, when caused to rotate, shear a mineral from the mine wall proximate to the cutter drums. A rack structure positioned along the mine wall face provides the drum cutter mining machine with a surface upon which translation of the mining machine along the wall face is allowed. U.S. Pat. No. 4,155,599 discloses drive gears which are positioned on the drum cutter mining machine to allow meshing with a rack structure.
U.S. Pat. No. 4,155,600 discloses a rack structure allowing engagement with the drive gears. Also, West German Patent Publication No. DE-PS 3008959 shows a rack structure. The rack structure is comprised of a plurality of movable and immovable rack segments, or sections, positioned end-to-end to provide surfaces allowing translation of a drum cutter machine positioned thereupon. Each rack segment is comprised of two longitudinally extending flat metal members between which discrete rack pins are disposed at a predetermined space from one another. The longitudinally extending flat metal members are of different thicknesses wherein the flat metal member which is positioned away from the mine wall has a thickness greater than the thickness of the flat metal member positioned proximate to the mine wall. The thicker flat metal member contains lug portions at each end thereof wherein the lugs engage with a bracket which is rigidly secured to a section iron of the side bracket of the rack structure. The lugs of the adjacent rack sections are disposed in a recessed portion of the bracket in pairs, and are retained by connecting pins which extend through bore holes extending through the lugs wherein the ends of the connecting pins also engage in bores in bracket walls of the bracket.
In mining operations, the rack segments must be capable of withstanding the forces caused by the weight of the drum cutter, and additionally, must be capable of withstanding the forces created during translation of the mining machine along the rack structure. The rack structures are effectively subjected to substantial tilting forces. Because of the one-sided mounting of the rack in which the thicker flat metal member essentially supports the rack, the tilting forces increase the likelihood that the thin flat metal member may become distorted or otherwise damaged, resulting in considerable impairment of the connection of the rack sections and the bracket.
It is therefore the object of the present invention to provide a rack structure for advancing a drum cutter mining machine which is less susceptible to damage caused by tilting forces created during movement of the mining machine.